Purpose To study the effects of ethoxyquin (EQ) and lycopene (LCP) supplementation on the growth performance, lipoprotein levels and antioxidant function of rainbow trout (Oncorhynchus mykiss) fed fish oil-based diets, in order to screen the suitable antioxidants for rainbow trout diets.
Method Three isoproteic and isolipidic diets were formulated to contain 0, 0.02% ethoxyquin and 0.02% lycopene, respectively. Two hundred and seventy rainbow trout with average body weight of (29.4±0.1) g were randomly divided into 3 groups (with 3 replicates of 30 fish each).
Result (1) Supplementation with EQ and LCP had no significant influence on the feed intake and daily gain coefficient of rainbow trout (P>0.05), FI and DGC in fish fed LCP diet were significantly higher than those in fish fed EQ diet. Supplementation with EQ and LCP significantly improved feed coefficient rate and protein efficiency ratio (P<0.05). There was no significant difference the two indexes between the two groups. (2) Supplementation with EQ and LCP had no significant effect on pepsin, intestinal and hepatic trypsin, hepatic amylase activities (P>0.05). Supplementation with EQ and LCP had negative effects on the intestinal amylase activity. Supplementation with LCP significantly increased the activity of intestinal disaccharidase (P<0.05). (3) Supplementation with LCP significantly reduced the serum total cholesterol, low density lipoprotein cholesterol, LDL-C/HDL-C and hepatic total fat content (P<0.05). (4) Supplementation with EQ and LCP significantly improved the plasma peroxidase and glutathione peroxidase activity (P<0.05). Compared with the EQ supplementation, the activity of plasma, liver glutathione reductase (GR) and hepatic lysozyme were significantly improved by LCP supplementation (P<0.05).
Conclusion It is concluded that the antioxidant capacity of rainbow trout is improved by ethoxyquin and lycopene supplementation. But lycopene as antioxidant was more conducive to improve its growth performance and antioxidant capacity.
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